Viscous fingering patterns that form in a Hele–Shaw flow are very well studied in fluid dynamics. These patterns, which arise due to the Saffman–Taylor instability [1]}, occur when a viscous fluid that fills a gap between two narrowly separated parallel plates is displaced by a less viscous fluid, which is injected into the cell. Provided these two fluids are immiscible, an interface forms which is usually unstable and develops visually striking patterns characterised by their branching morphology. As the governing equation for the velocity of the viscous fluid is the same as Darcy's law, Hele–Shaw flow can be thought of as a model for flow through a homogeneous porous medium. Further, the Hele–Shaw framework has also been used to model interfacial instabilities appearing in other scenarios including bacterial colony growth [2]}, crystal solidification [3]}, random walks, [4]}, and the flow of electrolytes [5]}, [6]}. We refer the reader to [7]}, [8]}, [9]}, [10]} for a historical summary and comprehensive overview of the broad applicability of the Hele–Shaw model.
